Embodiments of the present invention are related to valves designed for control of fluid delivery within industrial processes making semiconductor devices, pharmaceuticals, fine chemicals, and many similar fluid delivery systems. Controlled fluids may be liquids, gases, vacuum, vapors, or combinations of substances in those states. Fluid delivery apparatus intended for manipulating process materials within semiconductor manufacturing equipment usually require attention to maintaining high purity of the delivered reactants. Mechanical shafts sliding or rotating within a packing type of seal arrangement are known to often cause detectable particulate contamination of high purity process materials. Fluids that are radioactive, poisonous, pyrophoric, or otherwise dangerous, may also be thought less safe when handled in apparatus having packing type seals. U.S. Pat. No. 4,606,374 and U.S. Pat. No. 4,732,363 both issued to Terrence J. Kolenc, et al., are two examples of valves using metallic diaphragms (instead of packing type seals) for sealing the controlled fluid from the surrounding environment. A variety of actuator types, including manual, pneumatic and electric, may be used with diaphragm sealed valves as is well known. It is also known that actuators intended for simple on-off control of fluids as well as actuators designed for proportional, or modulating, control of fluid delivery within industrial processes making semiconductor devices may be used with appropriately designed diaphragm sealed valves.
Designers of valves for high purity applications generally are aware of many different approaches to providing a leak tight valve chamber sealing diaphragm. In U.S. Pat. No. 4,606,374 issued to Kolenc et al., a diaphragm comprised of three sheet metal discs is peripherally clamped between stepped structures in a valve body and a valve bonnet. In U.S. Pat. No. 5,145,147 issued to Nakazawa et al., a single layer sheet metal diaphragm is welded to a portion of a valve assembly. In U.S. Pat. No. 5,755,428 issued to Ollivier, a diaphragm is statically sealed against a valve body by a clamping member forcing the diaphragm against a toroidal-shaped projection on the valve body.
Various other developments in the field of diaphragms have dealt with material composition as described in U.S. Pat. No. 5,820,105 issued to Yamaji et al., diaphragm shape or contacting actuator as described in U.S. Pat. No. 5,851,004 issued to Wu et al., and U.S. Pat. No. 5,201,492 issued to Beauvir for example. Some designers have found considerable performance limitations associated with hysteresis of actuators and diaphragms themselves. U.S. Pat. No. 5,927,325 issued to Bensaoula et al. provides an example case discussing hysteresis in detail.